Testing system for automatic telephone switches



TESTING SYSTEM FOR AUTOMATC TELEPHONE SWITCHES Feb. 15 1927.

- H. w. MacDoUGALL TESTING SYSTEM FOR AUTOMATIC .TELEPHONE SWIICHES- Feb. 15 1 2 V 9 7 H. w. MacDoUGALL TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES Feb. 1s, 1927. 1,617,405

H. w. MacDoUGALL TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES I I I, Filled Deo. a. 1925I 5 sheets-sheet 5 o J oo oo A oo o oo ooo oo y l o oo oo o o 0 [l Y :a 1:3 o |::a o .DQ o

Patented Feb.. 15, 1927.

NANNY w. MACDOUGALL, or EAST ORANGE, New JNRsNY, AssieNon `To WESTERN ELECTRIC COMPANY, iNconronATnn, or New' Yoan, N. Y., A CORPORATION orv NEW YORK. v

TESTING SYSTEM roisv AUTOMATIC TELEPHONE swITcHEs.`

Application led Becember This invention relates to a telephone exchange system and more particularly to a testing device in a machine switching system for testing selector switch units.

Itis an object of this invention to provide an improved testing system.

The switching units vof an automatically operated telephone exchange are made up of control apparatus, relays and vauxiliary circuits to control its automatic progression and further control other switching units. A large number of 'such switching units arerequired in a system of this kind, any one of which may be arbitrarily selected, when idle, to complete a service connection. Thus, it is apparent that a switching,` unit giving inefficient service is not immediately noticed. Since the apparatus of a switching unit requires adjustments within limited variations, it is important that these units be regularly 'tested to determine'their ability to render etiicient service. duce the cost of suc-h maintenance, it is desirable to use a testing system requiring a limited amount of manual operation'.

A feature of this invention is in the use of a common'testing device. Y

A further feature of this invention resides in the provision of means for determining whether l'the brushes associated with the automat-ic switches are in contact with the terminals toV which they have been directed. A still further feature of this invention is found in the use of a testing device to determine whether or not the conductors of an automatic switch' are short-circuited or grounded.

Another feature of this invention is the provision of a testing device equipped with keys to function as the register of a sender, in combination with a progression switch, to automatically control the connection of a selector switch to either a test line or a subscribers line switch. The testing device remains positioned in such a manner as to receive a signal upon the completion of the tests. y

These and other features of the invention will he apparent from the following description vtaken in connection with the accompanying drawings. v

y Vhile the invention has been disclosed as particularly adapted for testing switches of the panel type, itwill be apparent from In order to re.

8, 1923. Serial No. 679,314.

the following description that the invention has a wider utility and that by slight modiiications it could be adapted for ltesting other types ofselector switches;

Figs. 1 and 2 show a testingV and controlling circuit for directing the incoming selector switch and the nal selector switch to either a test line or a subscribers line.

Fig. 3 shows the incoming Selector switch Y to be tested. Y A Y ,i

Fig. 4 shows Ya nal selector switch to be tested and to be connected to the wanted line.

Fig. 5 shows a line switch circuit associated with the subscribers station. It is f driven type in which a plurality of sets of brushes are mounted on a vertical brush shaft and arranged to be selectively tripped into` engagement with individual terminal banks. The brush shafts are propelled -in a vertical direction by means of constantly rotating power drums. In general construction and operation t-hese switches are both of the same character as the one shown and described in detail in Patent No. 1,123,696, issued January 5, 1915, to E. B. Craft and J. N. Reynolds. More specifically, the incoming selector shown in Fig. 3 and the final selector shown in Fig. 4 are described in the above mentioned patent to F. A. Stearn, et al.

The test man before proceeding with the test on an incoming selector inserts plug 234 into jack 304 and plug 232 into jack 231. Certain of keys .130 to 169 are then depressed to register the line number to which the sclector'switch is Yto bev directed. key is then actuated by the test man and yso Avv start from this point the operationis automatic until trouble is encountered or a signal'is received by the test man that the Vtest. has been successfully completed. A

Upon the actuation ofthe start key, a progressively operated switch is actuated and in its progressivevm'ovement, establishes circuits for directing the incoming selector swtich to yawparticular final selector switch and the final selector switchto a group of termina-ls which have been made busy by the insertion of a plug in a multipleV jack associated` therewith. I The incoming selector switch performs its usual functions when the busy line is en.- countered, that is, it provides a path over which a busy flash may be sent to the test circuit. Upon the reception of this fiash, the test man is in' Va position to know that the test has been successfully completed.

A test may be made on t-he final selector switch shown in'Fig. 4 bythe insertion of plug 234 in jack 453 and the actuation of certain of keys 130 to 169 todirect the final i selector switch to any subscribers line. The successful completion of the test is indicated .by the operation of a relay in a circuit whose battery and ground are supplied from the line circuit.

Having now described in a general way the apparatus employed in conducting tests and the manner in which it is to be used, it is thought that theinvention will be bet-ter understood by a consideration of the specilic manner in which it functions.

Brush continuity test of 'incoming selector. To initiate the test, plug 232 is inserted intojack 231, plug 234 is inserted into jack 304 of the particular selector circuit to be tested, and plug 444 is inserted into jack 445, the purpose of which is hereinafter described. The proper keys, shown 4in Fig. 1, tocontrol the incoming and final selector switches to select a line will then be depressed. l Assuming that the line to be selected is 3190, keys 133, 141, 159 and 160 will be actuated. The actuation of the above designated keys will associate certain of the counting relays with the terminals of the arcserved by brush 201, the functionino' of which will be described hereinafter. Srtart key 240 is now depressed to start the automaticprogression of switch 200. The operation of key 240 establishes a circuit which may be traced from grounded battery, winding o-f relay 213, operated contact of key y240, right armature and back contact of relay 212, conductor 209, normal contact of the arc served bybrush 204, to ground. Re-4 lay 213 is energized in this circuit. 1f the 212, to grounded battery. The energization of relay 212 establishes a circuit for lighting lamp 228 to indicate the busy condition, from grounded battery, resistance 223, lamp 228, right armature and front contact of relay 212, conductor 209, normal contact of the arc served by brush arm 204, to ground. The energizing circuit of 1 relay 213 is opened at the right' armature and back contact of relay 212 and this relay will not be actuated, preventing the procedure of test of a'selector switch that is busy. lf, however, the incoming selector switch shown in Fig. 3 is idle, relay 213 is energized over the circuit previously traced upon the operation of key 240. A locking circuit for relay 213effective on. the release of key 240, may be traced from Vgrounded. battery, through the winding of relay 213, left armature and front contact `of relay 213, winding of relay 217, right armature and front contact of relay 213, left l armature and back contact of relay 211, conductor 255, armature yand back contact of counting relay 11, to ground. Relay 217 is energized inrthis circuit, completing a circuit from grounded battery, winding, armature and back contact of magnet200, brush arm 203 and its associated normal contact, conductor 263, left armature and front contact of relay 217, armature and back contact of relay 220, to ground. Magnet200 interrupts its own circuit, stepping the brush assembly of the associated switch to contact 2.

A circuit may now be traced from grounded battery, winding of relay 221, y'conductor 264, brush arm 204 and its associated strapped contacts, to ground. Relay 221 upon energizing, connects to the testing circuit through its armatures, conductors 242 and 266, leading from the incoming selector. These conductors are normally open to prevent connecting a1 busy incoming selector switch to the test circuit. A circuit isV also completed for lighting4 guard lamp 229, eX- tending through resistance 224, lamp 229, conductor 265, to ground or brush 204. VMagnet 200 is again energized from grounded battery, winding, armature and back Vcontact of magnet 200, brush arm 203 and its associated contact 2, to ground. The' switch is thus rotated toposition 3. A circuit now extends from grounded battery, winding of relay .10, conductor 121, normal Contact of key 256, conductor 267, contact 3 of the arc served by brush 202, to ground. Relay 10 is energized in. this circuit andk connects grounded battery through its ve right armatures and back contacts to the windings of counting relays 0 to 9. At its left armature and front contact, it extends grounded battery over conductor 122 through the lwind.- ing of relay 220 to ground, energizing this Y relay. The energization of relay 220causes the energization of stepping magnet 200 through brush 203 and its associated conlun vfront contact oit relay 221,

ltact 3, armature and `front contact of relay battery, right winding of relay 311 in Fig.

3, upper contacts of sequence switch spring 321, resist-ance 315, upper contact ot sequence switch spring 324, tips of jack 304 and plug 234, tip conductor of patching cord 233, tips of plug 232 and ack 231, conductor 242, lett armature and front contact of relay 221, conductor 263, brush arm 206 and its associated contact 4, normal Contact ot key 256, conductor251, left winding of relay 214, winding of relay 215, conductor 123, armature and back contact of the 0 counting relay, conductors 124- and 254, inner lett armature and back contact of relay 212, conductor 235, normal contact ot key 256, conductor 252, armature and front contact of relay 221, conductor 266, rings of jack 231 and plug 232, ring conductor of patching cord 233, rings ot plug 234 and jack 304, lower contact of sequence switch spring 323, resistance 316, lower contact of sequence switch spring 335, to ground. Relays 311 and 215 are energized in this circuit but relay 214 is polarized in the opposite direction to the current flow and, therefore, does not energize at this time. Relay 311 in attracting-its outer left armature, establishes a circuit from grounded battery, winding ot the power magnet of sequence switch 300, lower contact of sequence switch spring 323, outer left armature and front contact or' relay 311, lower contact of sequence switch spring 322, to ground, for rotating this sequence switch out ot position 1 and into position 2. 1n position 2, a holding circuit for relay 311 may be traced from grounded battery, right winding of relay 311, right contacts ot sequence switch spring 321, right armature and front cont-act of relay 311, left contacts ot sequence switch spring 336, resistance 315, upper Contact of Asequence switch spring 324, tips of jack 304, and plug 234, tip conductor or' patching cord 233, tips or plug 232 and jack 231, conductor 242, left armature and front contact of relay 221, conductoi'263, brush 206 and its associated Contact 4, normal cont-act of key 256, conductor 251, lett winding oi' relay 214, winding ot' relay 215, conductor 123, armature and back contact oi counting relay 0, conductors 124 and 254, inner Vleft armature and back contact of relay 212, conductor 235, normal contact of key 256, conductor 252, right armature and 266, rings ot" jack 251 and plug 232, ring conductory of patching cord 233, rings ot plug 234 and jack 304, lower contact of sequence switch spring 323, resistance conductor 316, lower lcontact of sequence switch spring 335, to ground. lVith sequenceswitch 300 in position 2, a circuit is also established for energizing up-drive magnet '302. This circuit may be. traced from grounded battery, winding of Lip-drive magnet 302, upper right contact of sequence switch spring 334, outer left armatureand Y front contact of relay 311, lower contact of sequence switch spring 322, to ground. The selector switch elevatoris now driven upf ward in the well known manner and in its upwardr movement brush 341 is intermittently brought into contact with the conducting portion of commutator segment 344.

Thus, -a shunt circuit is established to cause the intermittent deenergization of stepping relay 215. Y This circuit may betraced from ground through the lower contact ot sequence switch spring 333, brush 341, commutator 344, lower contacts of sequence switch spring 336, to a junction point in the circuit established for energizing relays 311 and 215. The shunt circuit will not cause the release of relay 311, of relay 215. y

The initial energization ot relay 215 over the fundamental circuit establishes a circuit for energizing counting relay 1 from ground, armature and front contact of relay .215, conductor 253, brush 201 and its associated Contact 4, conductor 125, left operated contact of key 133, armature and back cont-act of countingrelay 1', winding of counting relay 1, conductor 175, outermost right armature and front contact of relay 10, to grounded battery. Counting relay 1, upon energizing, itself and an operating circuit ior countingl relay 1 through the winding of counting relay 1 and its` own armature andyfront contact to ground, which circuit becomes effectiveupon tlie first deenergization ot stepping 'relay v215. vThe upwardV move-` Vright armature and front contact of relay 10, to grounded battery for energizing counting relay 0. The upward movement of the incoming selector v switch elevator again establishes the shunt circuit, causing the release of relay 215. Upon the vrelease of relay 215, a circuit is vestablished,from i butwill cause the release establishes a 'locking circuit for iso rbattery'. Relays 0 and 11 are energized in this circuit. Y

The operation of counting relay 0 opens the fundamental circuit to cause the deenvergization ofrelay 311, which is effected as soon as brush 341 is moved to an insulated above the conductin' segment, which caused kthe second release of stepping relay 215,

Relay 311 upon deenergizing, opens at its outer left armature and front contact the energizing circuit for up-drive magnet 302, Vwhich deenergizes, causing the arrest of the upward movement of the incoming selector switch elevator. A circuit is also established from grounded battery, winding of the power magnet of sequence switch 300, upper left contact of sequence switch spring 323, inner left armature and back contact of relay 311, to groundV for moving this sequence switch out of position 2 and into position V3.

Relay 11 at its armature and back contact opens the holding circuit for relays 213 and Y217, which deenergize, and also establishes acircuit for actuating magnet 200. This circuit extends from grounded battery, winding, armature and back contact of magnet 200, brush 203 and its associated contact 4, conductor 245, armature and front contact of relay 11, to ground. The switch is thus rotated from position 4 to position 5. When brush y202 leaves terminal 4, the 'circuit through relay 10 is opened, causing this relay to deenergize, which in turn causes the deenergization of the .counting` relays and relay 220. The deenergization of relay 220 completes a circuitgfrom grounded battery, winding, armature'and back contact ofV magnet 200, brush 203 and its associated contact 5, armature and back contact of relay 220, to ground for rotating the switch from position 5 to position 6. Y

A circuit now extends from grounded battery, winding of relay 10, conductor 121, normal contact of keyl 256, conductor 267, contact 6 of the arc served by brush 202, to

ground for energizingrelay 10. l The ener-- gization of relay 10 re-establishes the circuit for energizing relay 220, which closes a circuit from grounded battery, winding, armature and black contact of magnet 200, brush 203 and its associated contact 6, armature and front contact-'of relay 220, to ground for rotating the switch from position 6 to position 7. With the switch in position 7. thefundamental circuit is again established for incoming group selection,

This fundamental circuit is the same as previously traced, with the` exception that position 3 of sequence switch 300 and contact 7 of the 'are served 'by brush 206 are used instead of position 1 and `contact 4,

respectively. Relays 311 and 215 are energized in this circuit. A circuit is then established from grounded battery, winding of the power magnet of sequence switch 300, lower contact of sequence switch spring 328, outer left armature and front contact of relay 311, lower contact of sequence switch spring 322, to ground for rotating this sequence switch out of position 3 intov position 4. rlhe holding circuit for relay 311 is again established in position 4 as previously traced, A circuit is also established from grounded battery, winding of tripvmagnet 303, right contact-s of sequence switch spring 335, to ground. trip magnety actuates the trip rod so that on subsequent upward movement of the incoming selector switch elevator, brushes 350, 351, and 352 will be broughtinto engagement with the bank terminals in the well known manner. A circuit is now established from grounded battery, winding of up-drive magnet 302, upper right contact of sequence switch spring 334, outer left armature and front contactof relay 311, to ground at the lower contact of sequence switch spring 322. The incoming selector switch elevator and commutator brushes are now driven in an upward movement causing brush 342 to engage the conducting portion of commutator 345 in order'to establish `a shunt circuit for deenergizing stepping relay 215. This shunt path may be traced from ground at the lower contact of sequence switch spring 333, brush 342, conducting portfon of commutator 345, upper right and lower left contacts of sequence switch spring 336, to a point of junction in the fundamental circuit Jwhere an effective shunt is placed around relayl 215.

The initial energization of relay 215 upon Athe establishment of the fundamental circuit, completes a cfrcuit for energizing counting relay 2. This circuit may be traced from ground through the armature and front contact of relay 215, conductor 253, brush 201 and its associated contact 7, conductor 269, right operated contact of key 133, left operated contact of key 141,

The energization of the l armature and back contact of counting relay 2, winding of counting relay 2, conductor 176, fourth outer armature and front contact of relay 10,- to grounded battery. The energization of counting relay 2 establishes a holding circuit for itself and an energizing circuit for counting relay 2 which is effective upon the release of relay 215 which deenergizes when relay 342 engages the conducting portion of commutator As the incoming selector switch elevator 7s driven in an upward movement, brush 342 intermittently engages with non-conducting and conducting portions of connnutator segment 345, thus causing the intermittent en'- erglZa-tion and deenergization of relay 215.

Counting relays 1, 1. O, O', andy 11 arc thusl operated'fin the well 'known manner.V

The energization ot counting relay O opens the fundamental circuit, causing the deenergization of relay. 311 when brush 342 reaches the next non-conducting portion of' commutator segment causing the release of relay 215 and the energization of counting lrelay 0. The deenergization of relay 311 arrestsV the upward movement of the incoming selector switch elevator and causesV the energization of sequence switch magnet 300 in a circuit which may be traced from grounded battery through the winding of thev magnet, upper left contact of sequence switch spring 328, inner left armature and back contact of relay 311, to ground. Sequence switch 300 is thusv rotated out oiP4 position 4 into position 5.

A circuit is now established from grounded battery, left winding of relay 311, right contacts of sequence switch Vspring 327', to ground for energizing relay 311, which in turn completes a circuit from grounded battery, winding of the power magnet of sequence switch 300, lower Contact of sequence switch spring 328, outer left armature andl front contact of relay 311, to ground at the lower contact of sequence switch spring for rotating this sequence switch out of position 5 and'into position 6. In position 6, the incoming selector switch is operated to hunt for an idle trunk leading to a `final selector circuit. Since the trunk hunting feature of thsincoming selector switch 1s described in detail in the previously men-` tioned Patent No. 1,395,977, it will not be described here, but it will be assumed that an idle final selector switch has'been found,-

causing the deeneigization of relay 311.

The deenergization of relay 311 completes a circuit from ground at the upper right contact of sequence switch spring 329, right armature and back contact of relay 311, right contacts of sequence switch spring 330, brush 350 to terminal for rendering this final selector busy to other hunting'incorning selectors. The deenergization of relay 311 also completes a circuit from grounded battery, winding of the power magnet of sequence sw'tch 300, upper left contact of sequence switch spring 328, inner lett armature and back contact ot relay 311, to ground for rotating the sequence switch out of position 6 and into position 7.

ln position 7 of sequence switch 300, a circuit is established tor operating relay 311` This relay may be traced from grounded battery, through the left winding of relay 311, right contacts of sequence switch spring- 327, to ground. Relay 311, upon energizing,

l closes a circuit from grounded battery, winding of the power magnet of sequence switch 300, lower contact of sequence switch spring 328, outer left armature and front contact of relay 311, to ground through the lowery traced from grounded battery through the;

right winding of relay 311, right contactsV of .sequence switch spring 321, rightarmaturel and front contact of relay 311, lower right contact ofsequence switch spring 331, brush 351, terminal 354, upper left and lower right contacts of sequence switch spring'421, re-

sistance 450, lower left contact of sequencel l switch spring 419, to ground. Y

The energization of relay 11, upon the completion of incoming selector switch group selection as explained above, closes a circuit from grounded battery, winding armature and back contact of magnet 200,v

brush 203 and its associatedfseventh Contact, conductor 245, armature and front contact of relay 11, to groundl for? rotating this.v

switch from position 7 to position 8. l When brush 202 leaves its seventh contact, the en-vr ergizing circuit for relay 10 is opened. The operated counting relays and relay -220 are then deenergized. A circuit for switch magnet 200 may now be traced `from ground through the armature and back contactlof relay 220, brush 203 and its associated contact' 8, armature, back Vcontact and winding of magnet 200, to grounded battery for rotating this switch from position 8 to position 9. In

this position, a circuit is again vestablished ior relay 10 over conductors 121 and 248; contact 9 of the are served by brush 202, to

ground.'v Relay 220 energizes as .before and magnet 200 rotates the switch tromr position 9 to position 10 ,in a circuit which mav be traced from grounded battery, winding,

armature* and back contact of magnet 200,

brush 203 and its associated contact 9, armature and front contact of relay 220, to ground. c

The fundamental circuit 4is now extended to the iinal selector switchk as shown inv Fig. 4. This circuit may be traced from grounded battery, left contact of sequence switch spring 416, right winding of relay 407,

lower left contact of sequence switchsprings` 418 and 422, terminal 355,- brush 352,' upper left contact of sequence switch spring' 332, resistance l315, upper right contact ,of sequence switch spring' 324, tips lof jack 304 and'plug y234tip conductor of patching.

cord 233, tips yof plug 232k and jack 231, conductor 242, left armature and front contact ofrelay 221, conductor 268, brush k206 and its associatedcontact'lO, conductor 251, left,A winding of relay 214, winding. of relayl 215,v

'of relay 407, lower left contacts of sequence actuation of relay 407, a circuit is estal -V lished from grounded battery, winding of the `power magnet of sequence switch 400, lower Contact of sequenceswitch spring 413, conductor 40S, lett armature andv front contact ot relay 407, to ground at the upper contact of sequence switch spring 410 for rotating this sequence switch out of position 3 and into position 4. The holdingcircuit for relay 407 as previously traced, is again established.

In positions 3 to 5, an obvious circuit is established for energizing trip magnet 404 to cause the actuation of the trip rod iin the well known manner. Brushes 437, 438 and 439 are now prepared to engage the bank terminals upon the subsequent upward movement of the selector switch elevator.

In position 4, a circuit is established from grounded battery. winding of the high speed up-drive magnet 403, upper right contact o1c sequence switch spring 426` conduct-or 408, lett armature andV front contact of relay 407, to ground at the upper lett contact of sequence switch spring 410. vThe selector switch elevator is thus driven in an upward movement to bring brush 432 into engagement with commutator Segment 435. The engagement of this brush with the conducting portion of commutator segment 435 establishes a shunt circuit for releasing stepping relay 215. This circuit may be traced from ground, through the upper left contact of sequence switch spring 419, brush 432, conducting portion or' coinmutator segment upper right contact of sequence switch spring 41S lower lett contact of Sequence switch spring 422. thence over the fundamental circuitcausing relay 215 to deenei'- gize. The initial energiZat-ion of stepping relay 215 complet-es a circuit extending from ground. armature and front contact ot' relay switch elevatorpbrush 432 is intermittently engaged with the conducting and non-cond citing portions of coinniutator segment 435, causing the alternate operation and re.- lease o'iE relay 215. The counting relays are Counting relay 9 ener-r energized due to the deenei'gization of relay 215 in the well known manner until all of the counting relays, including relay 11, have been energized.

The energization of counting relay opens the fundamental circuit, causing the, deenergization ot relay407 as soon as the shunt ground is'reinoved at conunutator 435. Relay 407 on deenergizing, arrests the upward movement of the tinal selector switch elevator and establishes a circuit for rotating th-e sequence switch 400 out ot position 4 and into position 5, which may be traced from grounded battery` winding of the'A power magnet of sequence switch 400 I vupper right contact of sequence switch spring Y413.v left armature and back contact of relay 407, to ground at the upper left contact of sequence switchv spring 410.

The energization of relayl 11 closes a circuit froin grounded battery, winding, arinature and baclr contact of magnet 200brush 203 and its associated contact 13, conductor 245, armature and front Contactof relay 11., to ground.` The switch is thus rotated :trom position 13 to position 14. and the energizing circuit'of relay 10 is opened. As a result, the counting relays "and relay v220 deenergize. A circuit is then established `trom grounded battery` winding` armature and back Contact of magnet 200, brush 203 and its associated contact 14,'armature and vbackl contact of relay 220, to ground for rotating this switch from position 14' to position 1.5. 1n this position. thevenergizing circuit torV relay is again established, in turn completing an obvious circuit torrelay 220. A circuit may then be traced from grounded battery, Winding,-armature and backcontact of magnet 200.` brush 203 and its associated Contact 15. armature and front contact of relay 220 for moving the switch from position 15 to position 16. With the switch in position 16, the fundamental circuit for final units selection isA reestablished. Y

V71th sequence switch 400 in position 5 a circuitis established from grounded battery left contact of se uence switch saring 416, right winding ot relay 407, lower lett contacts of sequence switch springs 418 and 422. and thence over the fundamentalL circuit through'the winding of relay 215. to ground at theV Contact ofseque'nce. switch snring 235 aspreviously traced. The energia-ation of relay 407 closes a circuit `from grounded battery, winding of the' power magnet oi, sequence switch-400- lower con-` tact of sequence switch spring- 413, left armature and trout contact of relay 407.iupper contact of sequence' switch spring 410n to ground for rotating this sequence switch out of 'position 5 and into position 6. in which a. holding circuit for relay 407 is again established as previously traced. rllie final units selection may now be made.

soi

Vith sequence switch 400 in position '6, a circuit is established tor the slow speed vup-drive magnet 402. This circuit'inay be traced from grounded battery, winding ot magnet 402, lower contact ot sequence switch spring 417, conductor 403, lett armature and tront contact of relay 407, to ground at the upper contact of sequence switch spring 410.

T he final selector switch elevator is now actuated, causing the upward movement of biusli 431 over commutator segment 434.

Since the final' selector switch is to be directed to the first or terminals in a group otv ten` the shunt circuit tor deenergizing A ductor 127, operated cont-act of key 160, conductor 110, winding of counting `relay 0,

conductor 175, outermost right armature and front contact of relay 10, to grounded battery.4 Counting relay 0 energizes in this `circuit and completes a holding circuit Vfor itself andan operating circit for counting relays 0 and 11 which is eiiiective upon vthe release ot relay 215. y

' Relay 0, upon energizing, opens the fundamental circuit, permitting the deenergization of relay 407 as soon asbrush 431 reaches a non-'conducting portion oit commutator segment 434. The upward movementof the selector switch elevator is then arrested and a circuit is completed from grounded battory, winding` of Vthe power magnet of sequence `switch 400, upper right contact ot sequence switch spring 413, vlett armature and back contact of relay 407, upper lett contact of sequence switch spring 410 to ground. y

Sequence switch 400 is rotated out of position 6 andinto position 9 under the control of sequence switch spring 409.

The energization ot relay 11 completes a Vcircuit from ground through the Varmature and front contact of relay 11, conductor 245, contact 16 ot the arc.Y served by the brush 203, armature, back Contact and winding of switch ymagnet 200, to grounded battery.

*TheV switch is thus rotated from position 16 to position 17 opening the energizing circuit or' relay 10. The deenergization ot relay 10 causes the deenergization of the counting relays and relay 220. A circuit now eX- tends from grounded battery, winding, armature'an-d bach contact ot switch magnet 200,

brush 203 and its associated contact 17,

armature and front contact ot relay 220 to ground, for rotating the switch from position 17 to position 18. Y 71th brush 206 in contact with contact 1S of its associated` arc it again establishes thetundamenta'l circuit, previously traced. The switchnow revmains iny position 18 to further Control the incoming selector switch of F ig. 3 as will be described later. n

It will be remembered that relay 407 upon deenergizing caused sequence switch 400 to be rotated to position 9. In position 9 a circuit may be traced trom grounded battery, lett'contact of sequence switch spring 410, right winding ot relay 407, lower right and upper lett contacts ot sequence switch spring 415 to ground through the right armature and front contact ot relay 400. Relay 407 is energized in this circuit and establishes a circuit troni grounded battery, winding of the power magnet ot sequence switch 400, lower contact ot sequence switch spring 413, lett armature and front contact of relay 407,v upper contact ot sequence switch spring 410 to ground tor rotating the sequence switch out of position 9 and into position 12V under the control ot the sequence switch magnet contact409.

As .sequence switch 400 leaves' position 81/2 the holding circuit for relay 311is opened and this relay deenergizes. This holding circ-uit, it will be remembered, extended trom grounded battery, right winding ot relay 311, right contacts of sequence switch spring 321, right armature and front contact oi' relay 311, Alower right contact of sequence switch spring 331, brush 351, terminal 354, upper left and lower right contacts of sequence switch spring 421, resistance 450 to ground through the lower lett contact of sequence switch spring 419. The deenergization'ot relay 311Vv completes a circuit from grounded battery, winding ot the power magnet of sequence switch 300, upperlett contact of sequence switch spring 328, inner lett armature and back contact ot relay 311 to ground, `tor moving this sequence switch out of position 8 and into position 9.

In position 9 of the incoming selector sequence switch, battery and ground are reversed with relation to the fundamental circuit. This is done to signal the controlling circuit in Fig. 2 when nnal lselectionshave been completed and relay 311 released. rlhis circuit extends from Vgrounded battery through the right winding of relay 311, lower contacts ot sequence switch spring 325, resistance 316, lower right contact ot sequence switch spring 323, rings ot jack 304 and plug 234, ring conductor Vof patching cord 233, rings ot plug l32 and jack 231, conductor 260, right armature and front contact of relay '221, conductor252, normal contact ot key 256.k conductor 235, inner lett arn'iature and back contact oit relay 212,

conductors 254 and 124, armature and back contact of counting relay O, conductor 123, winding of relay 215, lett winding relay 216,' condu`ctors'18'0 vand 110,winding of relay conductor Zonder.. fis olfVV the arc 'servedby brush y206, conductor; 268, left armature and front-Contact ofl relay 221, conductor 2112, tipsoi jack 231 and plug 232, tiplv conductoroipatching cord 233, tipsno' plug231lfand' ofjjack 204,

upper Contact of sequence switchspring. 324,',

resistance 315, ,left coi'itactsof sequence switch springV 336, to y ground at- 'the upper* contacts o'sequence switch spring-330. Re,

1357s 3111215.: and 214 relergized in this circuit.- --f l.. i

1 The energizatihonofrelay. 21.4` establishes. an, actuatingpath lor relay' 216 and a lock-v ing Vcircuit or'itselfwlii'chinay beftrac'ed from.. ground 4through `brush '204,1V and its associated contact, conductors, 26.9v yandl 265, armature and front contacto'yrelay214l through -tlie windings of relaysy 214v and 216 in parallelto grounded battery.V Relay- 216 establishes a circuitiroin, grounded` battery, resistance 225, lampV 230,*out`erriglit armaf ture fand front contact oit-relay2161normal Contact of Ikey l256, conductor 267, contact.

1S or" the are served by brush y202. to ground for lighting lampV 230 eas an indication to the 'test man-,of the .progressof the test. A- circuitis also completedA fromfground, arma tui-e and front contact of relay 215, conductorf253, brush 201V 'and its associated-V coi'itact`v` 18, inner left armature" and lfront contactv of ot counting relay :0, conductorv 175, voutermost right armature yand frontVv contactbfrelay 10 to grounded Y battery yfor .energizing counting relay O; It vshould be notedth'at relay 10 was I energized over conductor 121 to ground it-brush 202 as traced foiylam'p'y 230. Thev energization'of coiinting`relay 0l establishes valooking eircuitforitselfl and 'an` operatingcircuitfor counting relays 01' and 11. Relay 215 Vwhile energized, 'maintains' ashunt.4 circuit"aroundAv the windings of counting relays 0` and .11 until uponfurther advance of sequenceswitchr 300 as will lbe Vpresently described,relay 215 is `deener'gized; I

Returning toaligf3," a. circuit is estab-l lished upon the Aenergization Vof relay '311 c from grounded battery, winding' of `relay 310, upper riglitjcontact osequence switchv spring 326, .right armature and Viront con-1A tact 'et' relay 311,' upper. contacts of sequence switch spring 330 to ground." ARelay'310is 4 energized in this circuit andi completes'xa circuit'li'oin; grounded battery, winding'ff the power magnet'of Vsequence switch v300,

Aarmature and `front'r'contact of relay 310," left `'contacts of sequence switcl'i'- spring330' to ground lorrotatin'g'this sequence switch out ot' position 9 into position-10.' Assequencey switch' 300 leaves position 9, the

fundamental circuit"traced`V through `"relays I 214 an'df 215v is opened, de'energizin'gz f 215..V yCoi-.ainting-,relays"`0 and 1-1"arelV :then energized grounded battery, out- Vwindin'gfof polarifzedrelay 218, innerleft' y 105 erm'ost 'right armature fand `frontfcontact ofV relayt10,.windingof counting relay 0,;windings 4of .counting Yrelays 11; and,0 inparallel,

armature and ifroiitf.contact of counting "re-4y i lay 0 to ground. YThe energiza'tionv of count-1. ing r'elayO,l fcauses 'the .fundamental circuit to rjema'in ope-n until the :ControlA circuitI of Figs. 1 and: 2 is inpo'sitionv4 to further.. control the incoming 'selector of-,Fig 3. The ener-j` 75 circuitA forv energizing vmagnet, 2007-1`from, 'i

gization ofcountingrelay 11 establishes ground through tlie armature; and". front con `E tact'offfcounting relay 11, ,conductorl 2435, e

"contact-' 11S-oit then arc served by brush 203,l

armature; back 'contact and winding 'offmagl net 200 ytoiv grounded f'batterfy,fr rotating ythis switch-'from position .18 to position 19 which causes-'the release; of 1 relaysl 10, l220 j and f the y countingrelays as previously described# 1Q.

Vitlif brush 206 oncon'tact .19 whatis lmowii-asA trunk closure conditionl with',

relation VAto the incoming selector switch l of; Fig; y3 yis established.VThissimulates `the connection of Uthe incoming selector-switch', tothe alling'subscriber preceding the ring-f ing' of fthe" wanted' lsubscribers station. `The circuit established for' trunk closurel mayrbeltraced from" gifoun ded A battery, Tthrough ythe right winding of relay v311, upper .contactsl l osequence l switch springf` 321, resistanceI 315,5iippercontact ef: sequence switch 'spring 3211,tipmotfjack 3 044and ofplugf23ll,litip jV 232` `ancl"of'j`ack*l231, -coii`ducto1f242, left armature 'and' fro'iit15-contact' of relay` 221,: conductor 263, brush 206 andA its associa-ted' contact "19, conductor 259,y ,right armature and baelrcontaet of 'relay 2416, resistance 226,

armature and 'backVVV contact 'of relayf212, condi'c'ter235 normal VContact of key 256, conductor 252, right armature and front contaototielay`1221, conductor 266, ring o'jack 231' and of'plug 232, yring,` conductor of patcliin'g'j'cord 233', ring' of' plug 2311 and of jack-y ,conductor et` patchingfcordl 233, tipi of plu'gi Y 304, lowerfcontact'of sequence switch-spring ses, resistancefeie-tojground thi-Lough the lower contactof seqiiencefswitch"spring--335- n spring; '326,'ri'ght armature "and, front con-l gaf contacts of, sequence' switicir` spring. eee. elayr 310is'eli'ie'igized`r and eoiiipletes 'a' cirf' Y cuit from? grounded batterwin'ding "of thel power magnet- 'sequenqe switch Boo, i125 armature andlfront contact "ofre'lay310,

left .conta'cts'fof sequence switch spring 330j to ground-'for rotatingithis sequenoeswitch 11V out of, position V10-and into-position' 11.3. l f With sequence switch 300m `position.r 11,

iso

' a holding circuit for relay 311 in ay be tracedl .froni grounded battery through its left winding, arinature and .back contact oil-' relay 314, upperleft contact of .sequence switch spring 334',- outer left'. armature and f front` Vcontact/ of relayalll, upper contact of se-V quence switch 'spring 332, sleeve of 'jack 304 andioffplug 234, sleeve conductor of-patchingcord233, sleeveoflplug 232 andro-f jack ciated contact 19,wi.nding of. relay 219, .rel`

. `brush-.204'.4 to.. ground.

231,coniductor .207, vbrush205V and its assosistancel257, contact 19"of.the.arcserved by .Resistance- .257 is of Vlow A value and .resist-v ance 258 is high. v'A potentioineter is .thus forinedsothat relay. 219 .will'belenergized Y from either groundedebattery or ground on lay.r 219i completes an. obvious circuit for enei'- i fbe, fully described-later.

completedfrom .grounded battery, winding, '1 armature and back contact of magnet, 200,

l grounded battery, winding. of relay 310,` up- A Vitltrought-he contact-of key .208. Y

. Sequenceswitch. 300 does not reniaininA positionll hutfis. advanced tolposition 13 ,gi-zing. relay-.210.v Relayy 210-estalolish'es a circuit from grounded; battery, resistance 222,1`outerright armature and front.ciintactV of. re.lay 21.0, left armature andv back Contact.

offrelay236, lainp 227, armature and back Contact :of relay 218, lleft .armature and front Contact .offrelay 21.0y to ground, for lighting;

this; lamp. lTheiitility oithisflamp will A circuitl is, also brush 203 and :its associated icontact: 19,v lleft armature. andffront Contact of. relay 210 .tol

groiuidffor rotating this switch to position 20:, 1

l TheY switch is then advanced to position terminalv 2.0 `oij-the arc served by brush .203

bynieans .of-the action of interrupter 3017,- Relay, 310 yis -inergized in position 11 from prei'.legftfconftactof sequence switch spring 326, upperfcontactof '.interrupter-307 to,

f1 armature and, front contactof relay 12g VAs sequence switch-300 leaves..positionA z advancedy *toY positie .31.0, left, .Contactsof Sequence.. switch Spring S30-to ground foradvaiicing thissequence'k Vswitch out ci position 11u and into position 11, relayAA 310 is deenergized. Upon.'` the closure of),thelO-Xver-icnntact of interrupter 307, relay, 310. y is.v again energized inan Volo-L vivons.I Iia'nner.4 Sequence switch 300 is then.

1.1.1.3. over 'thesame nath Beredthatjsequenceswitch400 rotated roin p position. 9` toposltion 12uponi the energizav tion ofrelay 407 .Y As this sequence switch enters position 11 'a circuit inay betraced j Jfroin grounded battery, resistance Y'449,

sleeves of plug l444 and *of jack terminal: f

440, l. brush 437, right contacts v of sequence switch spring 420, right armature andwfront contact of relay 407 upper rightcontact of sequence switch spring 415, right winding'of" relay 407, lower left Contact" of sequence switch spring 418, upper left contact of se? quence switch -spring`422, winding ogrelay 405 to ground. Relay 407is heldenergized i and relay 405 is energized in this circuit "and the latterivopens atyits armature andback. Contact the holding circuit 'for relay'406f which thereuponV deenergizes. r 'The deenergi'zation of relay 406` causes sequence switch 400 .toadvance, upon arriving in position 12,

outofl this position and pintor' position 13 over a circufitwhichinay bertraced from grounded eoV tact-s offsequenceswitch spring 330.` A cir` I cuitis now completed from grounded battery, winding'oil the powerniagnet ofsc-` quence switch 400,'lower contacts oijpseqiience switch Spring 411, right arnfiafture'and-front f. Contact of-'relay 406- to ground foradvancing 21 heause'of lthe presence of ground onl oyer. thelowerrright contact of sequence switch" spring 414,j the left.- armature and front-contact of relay 407ito groundat the upper. contact of. spring-410 after sequence switch. 400i leavesy position 121/2. As sequence4 switch- 400 enters positionv 14, with relay 407 operatedia circuitniay be traced Y .n from. -groundedbattery, windingof 'downground; The-.eugeigization of relay 310 coin- 'pletesa ,circuitfroin ygroundedbattery, windingopfithe power: magnet of sequenceswitch drive inagnet 401, lower right contact left armature and .front contact of relay 407 toground-at' the upper contact of sequence switch. ,spring 410. I Thefiiial wselectorvswitch elevatoris caused to inovey in a downward direction vunder. the control oi magnet 40.1. vWhen. brush 432 engages coininutatory segment 436,.a circuitx may loe.` traced roin grounded.;y battery, winding of. the power. magnet. of'sequence switch 400, upper le't contactof--sequence switch spring 413, coin- Vinutato'r segnientf436, brush 432, .upper lei't contact offsequence-switch spring 419. toy ground, for. rotating thissequence switch ou'tofrposition 14,'and intoposition'17.r As this Asequence switch. leaves .position.14, the

:holding Ycircuit Ithrough the left winding votrelay 407 is opened causing this relay tov deenergizel Relay 407 now energizesand deenergizes alternately in response to, interrupter 451, the circuit yt'orrrelay 407 extend'- f ing from grounded'battery, lett-winding of relay 407, upper Contact ot` sequence switch spring 414, interrupter451 tojground. S relay 407 closes itsflett contact, a circuit is4 closed from ground through the rightwind-` Sing of induction coil V452. lower right conv tact of sequence switch spring 410, lett armature andl Jliront `Contact of relay v407, con? ductor 408, upper lett contact ot'sequence switch spring 426, resistance '450, lower right and upper lett contacts of sequence switch spring 421, terminal ,354, brush 351, upper left contact of lsequence switch spring 331, winding of relay 312, lower'right winding ot' repeating coil k305 to grounded hat' Atery. VAs relay'v407v closes and opens its- Vswitch spring 324, tipsiot' jaclr`304'andlplug 234, tip conductor of patching-cord"233,tip

of plug 232, and of 231,'con'ductor 242, f-

I left armature andfront contact o`f`relay221,"

conductor 268, brush206 and its associatedcontact 21, conductors'270 and 254,winding of relay 218, resistance 226,v contact 21'ot` the arc Aserved by brush 2041, vconductor 253, in-

" ner lei't Aarmature and frontkcontactofl'relay 2212, Vconductor 235, normal -co'nt'acttvoiiikey 256, conductor 252, right armature."andrefontr contact of relay'221, conductor 266, rings ,of jack 231 and plug 232, ring conductor 'of i patching cord 233,'rings'ot plug 234 and 304, upper right Contact of sequence switch"y spring 323, lower leftk winding of repeating coil y305, upper cont-a'ctsfoi:l sequence switch spring 325, resistance V316,l upper lettcontact Aoi. Ysequence switch Vspring 335 tov grounded battery at repeating coil Relay 218 'energizes and deenergi'zes Y inter-Vil mittently in turn causing lamp 227,'whi'ch* it will be recalledwas lighted,`totlash Vas an indication to the test man that the' ltest has been successfully completed.l 'The test man. upon observation of the flashing lamp operates disconnect key 241, establish-M ing acircuit for energizing relay 211 troni y. grounded battery, left winding of relay '211 to ground at the operated contact ot key 241. Relay 211, upon energizing', establishes a locking path for itself which may be traced from grounded battery through its iight winding and inner right armature and frontcontact, conductor 269 to ground through the contactsot the arcserved by brush 204. Re! lay 211also completes a circuit from grounded battery, winding, armature and back con-V tact `of's witch magnet 200,l `outer ght: arma# ture front contact ofirr'elay 211'togroundy `through the contacts of the'arc-servediffbv brush 204. Switch 200 is thus rotate'dftroiiif.'

position x21 tolpositio'n'22 and acircui'tf is Jchen established for; actuating switch mag-f net 200 from grounded battery through l.its Y winding, armature yandl back Contact to ground through brush 203 andits associated Contact 22.' `TheVswi'tcliis' thus its norinalposition. v f

Switch 200 in rotating to `normal posi-I returned. .to f? tion,open's all circuit paths to cause the de-' enero'izationgot all operated l1`-elays mftlie Y control circuit of Figq2. When lamp 22'? .asa'res'ult of the return of the circuitot' 2 to normal', "isextin'guished, plug. 232 is re-v nioved from jack 231, plug 234 is removed jack '445by the test-man. Relay 311,'whichv was "held energized .over theA sleeve 'circuit extending toa ground in Fig. 2"'is deener-r circuity is' then established*.fromY grounded battery, winding of thepo'wer magnet of sequence switch300, upper left contact of; sequence; switch jspring V328 ,to ground attthe inner-left' armature and back contact1ofrelay 311 fori-rotating this'sequence switch.`

troni positionl13 to position 18.5' In "position `from jack 304 and yplug 444is'removed from" vgizeduqoon therestoration of switch 200. fAl

18 a circuit 'isj established for downdrivel magnet7301 from grounded battery through the winding of magnet 301to ground at'thev Y right contactsv of sequence switch spring ,333; The incoming selector switch. elevatorlv is'caused'tomove'in a downward direct-ion.,v

When brush v342,engages commutator ,segff ment 346, a circuit is' established from groundedy battery, windingY of" the Ipower r contact ofs'equence switchuspring1328, coin-v v e mutatorsegment 346, brush 342,'lowe'r right Contact of sequence'.switchfspring 333 Vto' ground for rotating this sequence'iswitch out of position '1S-and intoits normal position 1. `Al/Vhen' sequence :switch"300lettl position v161/4, ground` Von sleeve 'brush-V 350 wast re` moved, causing fthe" deenergization fof relay v406 which had been heldin an operatedv position over the sleeve 'conduetorfextending to ground at .sequenceiswitch spring-.330.. Up-k 411 to ground `atfthe vright armature .and

baclr contact oi relay 406, rotating these-1 fquence vswitch into' position 18.\" \Since5the `ti'nalselectorswitch elevator has-previouslyz "been restored a circuit isnow. establishedv Grounded Ybattery through the wind-xV 1,

on the deenergization of relay 406 a! circuit L '1nay"be traced troi'n 'grounded battery ythrough the'windingof'the power magnet". fol sequence switch 400, 'lower right and-upg per leftcontacts of sequenceswitch spring ing of the power magnet of sequence switch;

400, upper left contact of sequence switchV spring 413, commutator segment 436, brush iiof 432, upperleft contact of sequence switch spring 419` to groundl for rotating this se- Y* quence switch out of position v18and into its normal positionV 1. a

This completes*l the description of a successful 'test of brush4 Vcontinuity on the incoming selector; A busy backtlash is the ini i dication that the call vhasV gone through correctlly Asince the lnecessary circuits cannotbe completed unless all i the kbrushes are in contact withtheir respective terminals.

' .Y Brasil, continuity test of final selector. n

l 'A` brush continuity. test may also :be made on a inal selector circuit, Vas Vshown in Fig. 4.v To make thistest, plug-232 is inserted'in Y .jack 231 and plug 234 is inserted in jack 453;V The selector: switch elevator of Fig. 4

' isfdirected to` any subscribers. line such as Vthat shown in Fig. and terminating in terv min'als`1427, 428- and-'429J In Fig. 1 keys 139,141, 159 and 168 are depressed to direct kthe-final selector to theline shown in` Fig. 5,

- forexample, as are-*also start key 24U-and iinal key'256. The operation of key 240 escui-t; It' vthe final selector switch shown in Fig.,4 is'found busy, relay 212 willrbe ener- Y Y :gized toground on conductor 454and lamp dition. It relay 212- isfnotfoperated, rel-ay V`2i28`willi be lighted to` indicate -the busycon- 213 is energized andl locked. as before described and. relay -217 is energized. Magnet 200 vis .then actuatedl to fstepthebrush as- -ffsembly o'flits associated. switch to position 2. yRelay 221V is energized over the; circuit `V previously traced and connectsgthe testing clrcultfthrough its armaturesto conductors.

242 and 266,.leading to theV inal selector.

Guard lamp v229 is `lighted, andl switch 200 isrotatedv to position 3. 'A circuit now eX `tends-'from grounded battery,.wind1ng, arf.

` matureV and#` back contact of lmagnet '200,

' together.

`Y ing brush selection are thusA passed over and' i Vextending .Y through its winding, armature. and backcontact, brush 203 and its asso-- '60 Aciated contact 5 to'ground `at the armature' operated cont-act of key 256, conductor 267,

"contact 3of.the'arc served by brush 202 to ground. position 3 toxposition 5 since contacts 3 and i Theswitch is thus rotated l.from

4 of the arc served by brush 202 are` strapped The positionsfor making, incomthis selection is not made; Inposition 5, magnet 200 1s again energized over a circuit and back contact vof relay 220, rotating the V.switchto position: 6. With the brush as-y sembly of this switchinypositions 6 and 7,

' .award ai brush 2,02 .i'S Yagain- Supplied `and 4.

ner/,1.1.05r

throughthe operated contact .of key 256 to magnet 200. The. switch is thus rotated from positionv6to posit/ion 7 and then to Vposition 3, since contact 7 is strapped-to contact 6 in the arc of brush 202. Ground at the armature and back contact of 4relay 220 causes'the switch torotate to position 9.

il/Vith the brushv assembly resting'inv position 9, a. circuit is established from grounded b'attery,iwinding of relayV 10, conductor 121, contact 9 of the arc served by brush 202 to ground. VRelay 10 energizes, closing an obvious circuit for the energization of relay 1,220, which causes magnet 200 to rotate'the switch to position 10 over a circuit which may be traced from grounded battery, winding, armature and back contact oi" magnet armature and front contact 'of yrelay 220 to ground.

The iinal selections may now be traced from grounded battery, left contact of sequence fundamental' y circuit for controlling V20,0, brush 203 and its associated contact 9,

switch spring 416, right winding of relay 407, lower left contacts of sequence switch springs 418 and 422, tips otjack 45,3 and plug234, tip conductor of-patching cord V233, tips of plug 232' and' jackf231, concluetor v242, leftvarmature and front contact of relay 221,7conductor 268,'.brush 206l and its 'Y associated'contact10, conductor 251,1left conductor 123, armature and back contact 495 winding ofrelay 214,"winding of relay 215,V Y

of'0" counting relay, conductors 124 and 254,

inner left armature andback contact .of relay 212, conductor 235, operated contact of key 256toground. Relays 407 and 215 are energizedin thiscircuit.

Relay v407the`n causes the energization of i relay 406 and sequence'switch 400 is ad-v vancedV into position2 in a. manner previously described. l Finalbrush `andtens selections are now made'and` the operation'v proceeds 1n the same manner as described for theprevious test with the switch con-` trolled by magnet 200. `in positions 10,V and 13andv sequence switch 400 in positions 2 tablished for making units selection through The fundamental circuit is .then esthe advance of the control `switch to position v 16 and the advance of sequenceV switch 400 to .position k6. Slow-speed updrivemagnet before described for advancing the final se` lector switch elevator. upwardly moving brush 43.1 over commutator segmentv Every time brush431 engages a conducting port-ion of lcommutator 434, a rshunt circuit vtor `deen'ergizing stepping relay 215 is established. This shunt path may be traced from ground through the upper 'left contact-i.

of sequence switch spring'l 419, brush 431,

` conducting portion of vcommutator segment .4:34, upperrghtand lower lettcgntacts of y402 is then Venergized inr the'rnarmerhereinL Y mature and front contact ot relay V10 to 'groundedfbattery Counting relay 8 enering circuit for itself and an' operating cir- `tor switch elevatorybrush 431 is intermitvtentlyengaged with the conducting and ment 434 causing the alternate operation and line, as shown in Fig. 5; "A vcircuit iscomyin the manner previouslydescribed; A cir- 'sequence switch spring 422, ythence over the fundamental' circuit, causing relay v 215 to deenergize. Y

n The initial energization of relay215, upon ythe establishment of the fundamental circuit, completes-'af circuit for energizing' -counting relayv 8. rlhis circuitunay be traced frein ground through the armature and `front contact of relay; 215, conductor 253, brush 201 and its lassociated Contact 16, conductor 127, operated contact of key y168, conductor 173, armature andv back contact `of counting relay` 8', winding of counting relay 8, conductor 179, innermost right argizes in this vcircuit and-establishes a holdcuit forcounting relay 8 which is effective 1 upon the irst release of stepping Arelay 215.

On theupward; movement ofthe final-selecnon-conductingportions of commutator segpleted fronr grounded battery, winding of thenpowe'r magnet of thesequence' switch 400, upper right contact of sequenceswitch spring 413, left armature and baci;` Contact of relay 407, upper left contact of sequence switch i spring410 toY ground for rotating Vthis. sequence switchA out; otpositionj 6 and into position 9 lunder the controlfotsequen'ce switchjspring 409. l A

The switch controlled lb'y' magnet' 200 then rotated from position 16y to position1'8 cuit may nowv bey traced 4from groundedV battery, winding, armature andback'contact of 'magnet 200, operated contact of key'256, cenductor 257, contact 18 ot the arc'served by brush/202 to ground. Magnet 200 is 'energized iii-'this circuit andthe brush'assembly ofthe associatedswitch 'is rotated to position 19.' VAs brush 205nioves-from contact 18 Lto Acontact 19 the holding circuit-for 'relay ',406 j which extends vthroughits left winding, armature and back' contact of relay '405, lett farmat'ure"andy front contacthotrelav" 406, rconductor 454, sleeveofjack'4537jantl 'of plug 234, sleeve conductoiffot' patching "into position 13.?

tra 23a leitete of 'png 2.32am fof jack 231, conductor 207 to Vgroiind through'l brush 205` and its Vassociated?'first 18 contacts is transferred through lcontact 19 otfthe are f served'by brush 205, through the ywindingoi'y relay 1219, fresistance 257, contact 19 of the arc served by brush 204, to ground. Relayl 219I is then energized.

V,In- `position 9v of sequence'switch` 400, a L

circuit may bei traced Afrom, grounded bat- 1 tery, lett contact ot' sequence switch spring 416, right winding ofrelay 407, lower right andi upper left contacts of-seoluence switch spring 415`to ground throughthe right arma-` f ture and front Vcontact of Vrelay `406 which,

it will beremembered, is locked to ground on sleeve conductor 454. 'Relay 407 is' energized'and establishes a circuit for actuating sequence switch 400, rotating it out `off positionf9 Vvand' into position 12'under the ycontrol Y of sequencev switch 'magnet' contact 409.

"Ixthe circuit'to which the final selector is connected `isidle` the circuity through relay 405; andthe lright winding off relayr 407 will y, beopened and the` 'latter f will deenergize.-V

`Since relay 406 is held "energized a circuit may be Ytraceditroin grounded battery, winding of the power magnet of sequence switch '400,"upperriglit contact of sequence switch spring 413.' left yarmature and backcontact "of relay 407, lowerv'left contact of'sequence switch spr'ing410, lright armaturer and front contact of relay 406 to ground for rotating this sequence switch out of position '12 and ,Y l'

y In lposition 13, 'a'circu'it" extends from grounc ed battery, through the winding of the power magnet of sequence f switch 400 lower contacts'of sequence switch f spring 411, right. armature 'and fronty contact of relay 406 toground, rotating'this sequence 1' `switch out of" position 13 and into position "141`In position 14 the energizing circuit for magnet 400 extends through the winding` vot' `the'y magnet, Vupper righty'contactjyof se- I Q quence switch springf41'3, left armature andV ,backl contact of'ielay407, upper Contact lof `sequenceswitchspring4107110 ground; The sequen'ce'fswitch isy thus rotated toA position I 15.l A"circuit now extends `from grounded Y battery, up'periright vContact of sequence switch 'spring416,rresistancesf424 and i 423;, lower contacts of sequence switch spring 420, f

brush 437,"terminal 427, conductor 521,"brush '510l and. its yassociatednormal contact, Vwindn ings ot relay 502,150 groundkfRelay y502 is energized? 1nV .tlnscn'cuit The idle condition 'ofthe linefisindicated to the testman yby the" steady illumination' ot lamp 227 which, it will be remembered Vwas lighted upon the operation offrelay 219.*'Key 243 is Y,then operated,A 'completing a. circuit 'from grounded battery,l right 'armature `and back Acontact of relay `236,1ar`npl 250,` operated centact4 of key: 2431to ground through the windfing of relay 246. 1 The enei-gizationV of relay 246 places relay 237lacross the tip andring.

conductors242'a'nd 266, in a circuit which may be traced from grounded battery, right 'windingv of rela-y 5.01, innermost lower arma- Vturecand b ,aclccontact of relay 502, conductorf503,"terininal428, brush 438,'upperL switch spring 410,'or rotatingthesequence .contacts of Vsequence switch spring 421, rings "of jack 453 and plug234, vring conductor of patching cord 233ringsof`plug 232 and iack231, conductor 271, operated contact of f key 243, winding of relay 237, operatedcon- ,leaf the. are .serva by'lbmshoe @die 4t`or268, left armatureA and front contact 'of relay 221,y 'conductor 242, vtips of ]ack 231 tact of key 243, right armature and front contact ef relay'246, conductor 259, contact and plug 232, tipn conductoro patching cord 233, tips, of plug 234 .and vjack Y453, lower contacts of sequenceswitch spring` 422, brush 439, terminal 429, conductor 504, upper armatureandfback contaet of cut-off relay 502 to, ground. Thiscircuit does .notl become leffective sinceit will be remembered that relay 502 isenergized, The testy man'may, tion isf arrested, and a circuit completed from [relay 502 is s hunted and theabove traced fc'irc'uitisl completedV for energizing relay at will,. f'giround test lterminal 427 whereby Y Y [237, Relay501, however, does not receive 'sufflcient current through its riglityvinding "to energize. The energization of relay 237 indicates that kbrushes 437, 438 and 439 are nnctledwith terminals 427, 42e and 429,

respectively, in the following manner. A

r circuit is completed from grounded battery,

winding ofrelay239, to ground at the arma'- turejandiiront'contactfof relay 237. Relay "239 is energized causing `in turn Vthe lighting lof, ,lamp 242140111 `ground@ battery,

contact of relay 239 asan indication that .the teistfhas been successfullyv completed.

The test,k man Hthen operates disconnect ykey 231 and plug 234 from jack 453. A The' Cirin thesameinanner asdescribedffor theprev 'ceding[test As soon as plug .234 is withdrawn tromk jack 453,l the. holding circuit forrelay 406 is vopened'-and'this relay de-` energitzs- A Grfiutmay then be ,traced Vfrom grounded battery, left winding of re- Y lay 407 j upper contacts oifseopuence switch spring 411 toi ground yat the right armature and v back lcontact of relay 406. Relay 407 is energized, in turn completing a circuit fromgrounded battery, winding Voi"l the pow- `er magnet of sequence switch "-400, 'lower j rightcontact of sequenceswitch spring 413,

'left' armature andfront contact of relay 407,

upper contact of 'sequence switch spring 410` Vto ground forrotating-this sequence switch out 'ofposition ,15, and into position 16. As sequence switch 400 leaves position 151/2l the energizinggcircuito'f relay 407 isopened and vthis relay deenergizes, f completing .a Y circuit from grounded battery, winding ,of vthe vpower magnet of sequence switch400, .upper to ground a t the upper contact of sequence switch to position 17. In position 17 the energizing circuit for magnet 400 may be traced through the winding o fthe'magnet,

lower righty andupper left contacts of `sequence switch spring 411`to ground at the lghbel'mature and back Contact of relay 406. Sequence switch 400 yis thus rotated t0 Positief; 1.8.- Ili position. 11.8 a Circuit' may be .tladgfroln'grounded battery ...Winding 0f, ClOWIIlriYe 'magnet 401.10wer 4colltact 0f Sequence Switch Spring. 422, upper'- leh C01 tactjof sequence switch spring 417, up'per left contacter rsequence Aswitch: spring419 I to' ground. The lselector V switch eleyator is driven in a downward directionnnder the controlof magnet'-401. lhen brush l 432 enga-ges commutator segment 436 its mo grounded batterypupper left contact of se quence, switchspring' 413, commutator segquence switch 4 00 isfrota-ted out of position 18 into its normal position 1,- deenergizing dewndriye magnet 401. rThis: completes cuit.

Test for p and slee/ve crosses.

' happens t that the `V tip yTand sleeie conductorsof a selector circuit inadvertentlycome `into contact wltheach other or are crossed a piece of sol d eror other metal. v,The 'result of such a cross mayobstruct the service upona-nu'inber of switches and Vcause a pile-up cond ition. The test for this V'condition Ywill now'be deseribed.A Keys 133, 141, 159 and 160 are operatedin Fig. 1

' 'todirect the selector toa testline, repre7 sented by terminals 442, 441, -and 440. Plug 448 is then inserted in jaclw445, plugf446 .isinserted `in jack'272, plug 234 is inserted lin jack 453.'.and plug 232 is inserted 4in ,jack

-231. VKeys 208, 240, 256V and 238 are then perated. The circuit then functions in the 4same manner as describedfor the brush continuity test ofthe linalselector with the ex- "ception that when the final selector switch Velevator shown in Fig. 4, comes to rest on terminals 442, 441 and'440,a busy condition onV that lneis not encountered and sequence switch 400 comes torestin position 15 vas described for thexbrush continuity test of` With the brush assemblyof the switch associatedwith mag-V net200injposition' 19 andsequence switch .400 in .pos'ition 15, the

scri'bedbelow.

the final selector circuit.

test proceeds as cle-- i brush continuity test onthelinal selector cir- Referring to Fig. 4, a circuit may be traced from grounded battery, upper right contact of sequenceswitchv spring 416, resistances 424 and 423, lower contacts of sequence switch spring 420, brush 437, terminal 440,` sleeve of jack 445 and'of plug 448, sleevef l terminal [441, brush v438fupper contacts of Y. sequence switch" spring 421, ring ot jack conductor (of patching cord 447, sleeve of plug 446 and of jack 27 2, operated contact of key 238, left winding of relay 236 to ground for energizing relay 236.V AIt will be recalled when brush. 205 stepped to contact 19, relay 219 was energized,lin turn Acausing `the energization of relay 210. YRelay 237 is then energized in a circuitv from ground, left armature and 'frontcontact of relay 210, normal contact of key 243, wind-V l ing of relay 237, normal contact of key 243,

operated contact of key 238 to grounded battery at theright armature and frontl contact vof relay-236. The energization of relay; 237 causes the energization of relay 239 in acircuit extending from grounded battery, winding of relay 239 to ground atv the armature and front contact of relay237. Relay 239,

= upon energizing, provides a holding` circuit for relay 237 extending vfrom grounded battery, right4 armature and frontV conact ot' relay 239,- normal cOntactofkey243, winding of relay'237, normal contact of key 243 to ground at the vleft armature and, iront contact of relay 210. This holding circuit becomes effective lfor maintaining relay 237 energizedupon thevrelease of relay 236'.V If

vthe tip and sleeve yofthe iinal selector cir-l cuit are crossed, a circuit may betraced from ground,` inner lett armature and front contact of relay 239, normal contact of key 243,

l left armature and back-'contact of lrela-y 246,`

conductor 242tip ofjack 231 and yoi" plug 232, tip conductor of patching cord 233, tip

of plug 234 and of jack 453, lower contacts oi'k sequence switch spring 422Vbrush 439, terminal 442, sleeve oit' jack 445 and of plug 448, sleeve conductor ofV patching, cord 447,

F sleeveof plug 446 andl jack 272,` operated vcontact Yof keyV 238,V through theleftwinding or relay 236 to ground. The left winding of relay 236 is now Vconnected to groundfon both sides and this relay is deenergized.- A circuit may thenbeJtraced from grounded battery,` resistance 222, outer right armature and front contact of relay 210, left arma ture and back contact of Vrelay, 236Y lamp 227,-armature and back contact of relay 218, left armature and front contacto relay 210,

to ground, relighting lamp 2271 :A .circuit also v'extends from grounded battery, right armature and back contact of relay 236, 4lamp 250normalcontactof key 243, outer left armature and front contact of relay 2391to ground at4 the normal 'contact of key 241. Lamp 250 is lighted as an indication to the test man that the tip and sleeve of the final selector circuit. are crossed. If the crossed conditiondoes'not exist, the circuittracedV frorshunting relay isopen andthislrelay 'remains energized.` A" circuitthereftore extends' from ground through lnterrupter 2.7 3, Vnormal contactof'key 241, ringof jack v2:72v

and o'zt plug 446', ring conductor' of vatching cord '447, rings of plug 448 and]ackf445,

453, and of plug 234, ring conductor of patchi-ng cord 233, ring of `plug 232, and of jack"2`31, conductor 266, right armature 'and "front contact of relay 4221,A conductor 252,

lamp v274, left armature and` front rcontact of relay 236 outerright armature and front contact of relay ,210, resistance l222, to

groundedl battery. Lamp V247-4 is caused to flash in response.. to interrupter 273,'V kas an indication to thegtst man "that a crossed CfOnClition does4 not exist Y l The circuits, are now `restoredtonormal.

in an obvious manner uponthefwithdrawal ofthe plugs from their)respectiv'ejacks and the -.r'estoration o'f'all operated keys. 1

l/Vhile 'the'.r brusli continuity test'ha'sbe'n i described for use in connection with the final and incoming selector' circuit,.it is apparent that with slight modifications it'can also be applied to oce selector circuits such as areshow'n in Fig. l3 of Patent 1,395,977, issued Novembe'r'l,1921,'l to F2151. Stearn, et al.

However it is not thought necessary Vfor a 'complete understanding of the inventio'nto describe they test as applied to such selectors.

Vhat is clai'm'edis:

1. `In a telephonek exchange 'system in which sets' of terminals l,to ywhich are -connectedthe linesla'nd line apparatus associatedA with: subscribers stationsare caused l minals,"andl means for denoting that said brushes are` in contact with saidteirminalsl.

ics f `2.'In a Ytelephone exchangej-syste1nin which setsorn terminals to which `are icon? nected the lines and line apparatus asso-k ciated 'withsubscribers7 stations .are caused to he selected bymeans ofbrushesassociatedV H ,with selector switches, a testing device for ltesting said `selector switches comprising,

Vmeans -tof direct the brushes `of. any one `of said switches to engagea fset ofsaid ter-v i minals, and a relay operative over a circuit .extending through the Vcontacts of said l .brushes with saidterminals to controla signal as 'an indication thatsaid brushesare in contact "with said terminals,

3.111 ta. telephone exchange system" in nected lines to subscriberslstations and auxniliary apparatus are caused to be selected Ywhich sets ot' terminals ,tov which arecon- 

